Safety mercury switch



Aug- 11, 1959 s. R. MATTHEWS ETAL 2,899,522-

' l SAFETY MERCURY SWITCH Filed Dec. 8, 195B fig-2 52 Unite Patented Aug. 11, 1959 his SAFETY MERCURY SWITCH Stanley RtMatthews, Thomas Si. Darlington, and Melvin G. Sheets, Winston-Salem, N.C.

Application December 8, 1958, Serial N0. 77 8,77 16 2 Claims. (Cl. M10-152) This invention relates to switches and more particularly to switches embodying a pool of mercury, said pool of mercury making contact between the respective poles of terminals of the switch, the switch being so arranged that upon tilting of the same the mercury making the contact is drained from the mercury receiving chambers therein to interrupt the electrical circuit.

The main object of the invention is to provide a mercury switch of this type wherein both the electrical contacts between the battery and the ignition system and likewise between the battery and the generator are broken upon the tilting of the switch to an unusual angle.

Another object of the invention provides means whereby when the mercury is displaced from the recess ibetween the battery and the ignition, as by abnormal tilting thereof, the mercury leaves the recess or chamber in which it was trapped and moves to an annular channel and, under normal conditions, will not ilow back to its original recess to complete the circuit in the electrical system.

Another object of the invention is to provide a dammin'g means which can manually be turned to block the outermost channel and in consequence of which the mercury, which has been displaced from its normal recess or chamber to produce the contact between the respective poles, can be directed lback to its normal position, when the dam is manually operated and only when such manual operation is followed.

It has been found that in switches of this type that lit is Very desirable, in the event that the automotive vehicle overturns, that not only the electricity passing through the cables from the' battery to the ignition system be' broken, but also that the circuit from' generator to ignition system be broken, but on many occasions it has been determined that fires have been caused, in the event of accident, by the sparks emanating from the generator or from the eurrent passing through frayed wires of the generator system and from the motor continuing to run. Thus', the present invention automatically disconnects both the electrical ignition system and the electrical system to the generator.

Various other advantages and features of the invention will become more apparent when considered in the light of the accompanying drawings in which:

Fig. 1 is a front face view of this switch;

Fig. Z is an elevational rear view of this switch;

Fig. 3 is a top plan View of this switch;

Fig. 4 is a section on the line 4 4 of Fig. 5;

Fig. 5 is an inside face View showing the interior of the switch;

Fig. 6 is an inside face view showing the switch in tilted position wherein the contacts are broken; and

Fig. 7 is a simplied diagrammatic sketch of the wiring system of an automotive vehicle embodying the switch in the same.

Referring to the drawings, in which like numerals indicate similar parts throughout the various views, the switch is shown as comprising a front or face casing 6 and having attached thereto a usual battery clamp, generally indicated at 7. The face plate is' also provided with terminals 8 and 9 and likewise with a damming screw 10. The face plate of the switch is made of an insulating material, such as Bakelite or other well known plastic. The 'rear face of switch 11 is a relatively thin sheet of metal and has formed therewith a terminal 12 and is held to the rear side of the face plate as by screws 13 which pass through the plate and engage in threaded recesses 14. By' reference to Fig. 2, it will be seen that the plate is so iixed and held to the face plate by screws Which form in effect a triangle so that the rear plate can be reversed, that is, turned end by end, so that the terminal 12 can be projected from whichever side of the switch Ibecomes most convenient. The rear plate of the switch and the front casing of the face plate have interposed therebetween a usual type washer separator 15.

The terminal 7 extends inwardly from the face plate of the switch in a reduced pole portion 16 to cooperate with a chamber 17, said chamber being supplied with a sufficient amount of mercury 18 to make a contact between the pole 7 and the` back plate 11. The chamber 17 has extending upwardly therefrom when the switch is in its normal position and communicating therewith channels 19 and 20 and is further provided 4with channels 21, 22, and 23, which extend from the upper side of the chamber 17 to permit mercury to ilow therethrough and be directed towardy the channels 19 and 2li when the switch is turned to a suihcient angle. The mercury leaves the chamber 17 and passes through these respective channels to be trapped in an annular recess 24, said recess or channel extending completely around the inner circumference of the face plate of the switch.

Extending through the face of the switch is a damrning screw 10 being provided with an enlarged slot or kenf 30 which in one position of the screw registers with the re-v spective portions of the annular recess 24 and when so positioned, the mercury which is trapped in this recess is capable of movement through the slot and around the channel. This is the normal setting for this damtning screw and it will be seen that in the event that the switch is tilted beyond a reasonable position, that the mercury will leave the chamber" 17 by way of the various channels and ruri to the annular channel' 24 and whenthe mercury is in this'r channel, the same cannot be'revurn'ed to the chamber 17 by rotation ofthe switch becausel if the switch is rotated, the mercury simply rulns around the channel 24. In the event that it is desired that the mercury return-'to the chamber 17 and thereby remake the contact between the battery and the ignition system, it is necessary to manually turn the screw in' which position the serew plugs oir or dams the recess or channel 24. Now, `when the channelis dammed, with the switch valve 10' `at eleven oclock or vertical position, slowly rotate clockwise 360 returning valve 10 to the starting position, during course of which the mercury, which was formerly in channel 24, will |gravitate down' the channel' 19' and back into the chamber and thereby re-establish electricalV con-4 tact of the system.

The switch is further provided with a recess 25, which is bounded by walls 26, 27, and 28. The terminals 8 and 9 extend through the front of lthe casing and terminate flush with the rear side of the recess 25. A portion of mercury 29 is trapped in the recess 25 and, of course, extends to gasket or separator which faces back plate 11 and the front surfaces of the terminals 8 and 9 whereby to complete the circuit from the generator to battery. In the event that the switch is tilted to an angle of say approximately 90, the mercury separates and falls to one side of the recess and in consequence thereof breaks the circuit between the terminals 8 and 9 and therefore interrupts the electrical circuit from the generator to the ignition system. It will, of course, be understood that the portion of mercury 29 trapped in the recess 25 is always trapped there and can never be removed without taking the switch apart.

In the operation of the described switch, it is normal to ll both the recess 25 and chamber 17 with mercury at the place where the switches are made before the back plate is fastened in place. With this being done, lif the switch is turned 90 more or less in either direction or at least tilted until the mercury within the chamber 17 runs through the passages 19, 20, 21, 22, and 23 into the annular channel 24 and the damming screw 10 is positioned so that its slot 30 is positioned in registry with the channel 24, the mercury is in effect trapped in the channel 24 until the switch is to be used. When this occurs, the damming screw is turned 90 to thereby block the channel, after which the switch with its valve 10 in eleven oclock position is rotated to the right or clockwise 360 back to starting position and hereupon the mercury will leave the channel 24 and return to the chamber 17 to thereby make contact with the reduced end of the terminal 16 and the metal back plate 11. In this connection, the switch is ready to be used and the same is incorporated in the electrical system of an automotive vehicle. Thus, the mercury switch female terminal connector 7 is attached to the positive post of the batteiy and the engine ignition system wire 31 is clamped to the terminal 12 and from there the ignition wire 31 passes through the normal switch, through the wire 32 and back to the negative post of the battery. Likewise, an electrical wire 33 is extended from the positive post of the battery to the switch terminal 9 and an electrical wire 34 is attached to the switch terminal 8 and extends from this terminal to the generator 35.

When the switch is shown embodied in the electrical system of an automotive vehicle, it will readily be seen that upon the automobile being in an raccident wherein the same overturns or is tilted on its side, that the mercury in the chamber 17 will pass through the respective channels into the annular chamber 24 and with the darnming valve 10 positioned so that the slot registers with the channel 24, ywhich is the position in which the valve 10 is turned during normal operation of the switch on the vehicle, that the mercury after leaving the chamber 17 is trapped in the channel 24 and cannot be'returned to the chamber 17 to make an electrical contact between the pole piece 16 and the back plate 11. Therefore, it will be seen that in the event that the vehicle should overturn and right itself, that under these conditions -there would be no possibility of the mercury returning to the chamber 17 to re-establish the electrical circuit from the battery to the ignition system.

In order to reset the switch, it would be necessary to rst remove the switch from the vehicle and thereafter to manually turn the valve 10 to plug the channel 24, whereupon the switch could be manipulated to return the mercury to the chamber 17 and re-establish the electrical circuit. Of course, when the vehicle is turned to a 90 angle or actually overturns, the mercury trapped in the chamber 25 has been moved to a position to interrupt the circuit from the generator to the ignition system because in this position of the switch the mercury spanning the contacts 8 and 9 has been displaced so that the circuit is broken and the generator has stopped. In the event that the vehicle righted itself, the mercury would in this position break the contacts 8 and 9, but in view of the fact that the electrical system to the generator has once been broken, then the generator would not start itself again.

It will thus be seen that we have lprovided a novel switch which not only breaks the electrical circuit between the battery and the engine starting and lighting and ignition system, but likewise breaks the circuit sufficiently to stop the operation of thc generator and therefore eliminates the hazard caused in the event that the generator continues to run, the latter of which is not unusual in an overturned vehicle.

The invention is not limited to the exact construction shown but is capable of variations within the scope of the following claims.

We claim: Y

1. A safety switch for automotive vehicles comprising in combination a front casing of insulating material and a `rear plate of metal, the front casing within its inner face having an enlarged cavity and a terminal piece extending through said casing into said cavity, a portion of mercury lying in the cavity, a plurality of channels communicating `with the sides and upper portion of the cavity, an annular channel formed in the face of the casing and cornmunicating with at least one of the channels, a second mercury receiving cavity located above the first mentioned cavity, a pair of terminals extending through the casing and terminating in spaced relation in the second cavity, a portion of mercury in the second cavity, the metal rear plate secured to the rear side of the front casing and provided with a terminal, the mercury in the lower cavity l providing electrical connection between the terminal extending through the casing and the rear plate terminal, and a valve extending through the front casing and terminating within the annular channel, said valve having a slot therein, said slot registering with the annular channel in one position and blocking the channel in another posiiton.

2. A safety mercury switch for automotive vehicles comprising in combination a front casing and a rear metal plate attached to the rear side of the front casing, said front casing having an upper and a lower mercury receiving chamber formed therein, a pair of spaced terminals extending through the casing and terminating in the upper chamber, a single terminal extending through the casing and terminating in the lower chamber, a wall extending completely around the upper chamber to conne the mercury therein, an annular mercury receiving channel in the front casing, a plurality of mercury passages communicating with the lower chamber and the annular channel, a damming valve having a slot therein,

' said valve adapted to be turned to either register with the channel or to block the channel.

References Cited in the le of this patent UNITED STATES PATENTS 2,744,175 Moore May 1, 1956 

